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1. A) 225886 + 779 × 8

= 225886 + 6232

= 232118

B) 125 × 5 × 20 × 8

= (125 × 8) × (5 × 20)

= 1000 × 100

= 100000

C) 47286 : 2 + 14765

= 23643 + 14765

= 38408

D) 91428 - 23560 : 5

= 91428 - 4712

= 86716

3. A) 36 × 532 + 63 × 532 + 532

= 532 × (36 + 63 + 1)

= 532 × 100

= 53200

B) 679 × 123 + 679 - 679 × 24

= 679 × (123 + 1 - 24)

= 679 × 100

= 67900

C) 245 × 327 - 245 × 18 - 9 × 245

= 246 × (327 - 18 - 9)

= 245 × 300

= 73500

2. A) 6 × (x + 9845) = 29042

x + 9845 = 29042 : 6

x + 9845 = 14521/3

x = 14521/3 - 9845

x = -15014/3 < 0

Em xem lại đề vì lớp 4 chưa học số âm

B) (x : 3) × 8 = 8 × 3198

x : 3 = 3198

x = 3198 × 3

x = 9594

3. Tính bằng cách thuận tiện nhất

A, 36 x 532 + 63 x 532 + 532

= (36 + 63 + 1) x 532 = 100 x 532 = 53 200

B, 679 x 123 + 679 - 679 x 24

= 679 x (123 + 1 - 24)

= 679 x 100 = 67 900

C, 245 x 327 - 245 x 18 - 9 x 245

= 245 x (327 - 18 - 9)

= 245 x 300

= 73 500

Bài 2:

a: \(6\cdot\left(x+9845\right)=29042\)

=>\(x+9845=\dfrac{29042}{6}=\dfrac{14521}{3}\)

=>\(x=\dfrac{14521}{3}-9845=-\dfrac{15014}{3}\)

b: \(\left(x:3\right)\cdot8=8\cdot3198\)

=>\(x:3=3198\)

=>\(x=3198\cdot3=9594\)

Bài 1:

a: \(225886+779\cdot8\)

\(=225886+6232\)

\(=232118\)

b: \(125\cdot5\cdot20\cdot8\)

\(=\left(125\cdot8\right)\cdot\left(5\cdot20\right)\)

\(=1000\cdot100=100000\)

c: \(47286:2+14765\)

\(=23643+14765\)

=38408

d: \(91428-23560:5\)

\(=91428-4712\)

=86716

a/\(4,19\times50-132:\dfrac{2}{3}\)
\(=209,5-198\)
\(=11,5\)
b/\(637,38:18\times2,5\)
\(=35,41\times2,5\)
\(=88,525\)
c/\(56,32-13,4\times2,4\)
\(=56,32-32,16\)
\(=24,16\)
d/\(\dfrac{2}{5}:\left(\dfrac{4}{5}-\dfrac{1}{2}\right)\)
\(=\dfrac{2}{5}:\dfrac{3}{10}\)
\(=\dfrac{4}{3}\)

a: \(P=\dfrac{x+5\sqrt{x}-10\sqrt{x}-5\sqrt{x}+25}{\left(\sqrt{x}-5\right)\left(\sqrt{x}+5\right)}=\dfrac{\left(\sqrt{x}-5\right)^2}{\left(\sqrt{x}-5\right)\left(\sqrt{x}+5\right)}=\dfrac{\sqrt{x}-5}{\sqrt{x}+5}\)

b: Khi x=9 thì \(P=\dfrac{3-5}{3+5}=\dfrac{-2}{8}=\dfrac{-1}{4}\)

c: Để P=1/2 thì căn x-5/căn x+5=1/2

=>2 căn x-10=căn x+5

=>căn x=15

=>x=225

a) A = (x - 5)(x² + 5x + 25) - (x - 2)(x + 2) + x(x² + x + 4)

= x³ - 125 - x² + 4 + x³ + x² + 4x

= (x³ + x³) + (-x² + x²) + 4x + (-125 + 4)

= 2x³ + 4x - 121

b) Tại x = -2 ta có:

A = 2.(-2)³ + 4.(-2) - 121

= 2.(-8) - 8 - 121

= -16 - 129

= -145

c) x² - 1 = 0

x² = 1

x = -1; x = 1

*) Tại x = -1 ta có:

A = 2.(-1)³ + 4.(-1) - 121

= 2.(-1) - 4 - 121

= -2 - 125

= -127

*) Tại x = 1 ta có:

A = 2.1³ + 4.1 - 121

= 2.1 + 4 - 121

= 2 - 117

= -115

a) (2/5 x 25/29) + (3/5 x 25/29)
= (50/145) + (75/145)
= 125/145

b) (5/2 x 3/7) - (3/14 : 6/7)
= 15/14 - (3/14 x 7/6)
= 15/14 - 1/2
= (30/28) - (14/28)
= 16/28
= 4/7

c) (15/4 : 5/12) - (6/5 : 11/15)
= (15/4 x 12/5) - (6/5 x 15/11)
= 180/20 - 90/55
= 9 - 18/11
= (99/11) - (18/11)
= 81/11
= 7 4/11

a) (2/3) + (20/21 x 3/2 x 7/5)
= 2/3 + (60/210)
= 2/3 + 2/7
= (14/21) + (6/21)
= 20/21

b) (5/17 x 21/32 x 47/24 x 0)
= 0

c) (11/3 x 26/7) - (26/7 x 8/3)
= (286/21) - (208/21)
= 78/21
= 3 9/21
= 3 3/7

a) (25/8) : x = 5/16
=> (25/8) x (16/5) = x
=> 4 = x

b) x + (7/15) = 6/15
=> x = (6/15) - (7/15)
=> x = -1/15

c) x : (28/49) = 7/12
=> x x (49/28) = 7/12
=> x = (7/12) x (28/49)
=> x = 1/2

a) 6 x x = (5/8) : (3/4)
=> 6x = (5/8) x (4/3)
=> 6x = 20/24
=> 6x = 5/6
=> x = (5/6) / 6
=> x = 5/36

câu,b,không,đủ,thông,tin,nhan,bạn.